Diffusional effects in TGA gasification experiments for kinetic determination

Ollero, P.; Serrera, A.; Arjona, Rosario; Alcantarilla, S.

doi:10.1016/s0016-2361(02)00126-6

Cited by 163 publications

(95 citation statements)

References 8 publications

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“…For example, the rate of diffusion of material (reactant) may play an important role in the behaviour of reaction. Thus, the successful design of a gasifier, as well as its modelling, requires reliable kinetic data [9]. Fundamental to the combustion or gasification rate are the rates of pyrolysis and char oxidation.…”

Section: Introductionmentioning

confidence: 99%

“…The standard method of measuring these rates is via thermogravimetric analysis (TGA) under inert and oxidizing conditions, whereby a small sample of the feedstock (5-15 mg typically) is heated at a certain rate while simultaneously recording mass, time and temperature. TGA is used extensively to study the kinetic parameters of gasification of biomass with CO 2 as a function of mass loss [9][10][11]. TGA can be considered to be a fixed reactor technique with a relatively low heating rate compared to larger scale systems where biomass is added directly to the reactor at the reaction temperature so the particle heating rate is significantly greater.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and Performance of Raw and Torrefied Biomass in a Continuous Bubbling Fluidized Bed Gasifier

Al-Farraji

Marsh

Steer

et al. 2017

Waste Biomass Valor

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This paper is an experimental study of the kinetics of gasification of olive kernel by using a thermogravimetric fluidized bed reactor technique. Gasification of 'as received' and torrefied olive kernels were investigated in a lab-scale bubbling fluidized bed gasifier, operating at up to 3.2 kg/h. The effect of bed temperature between 550 and 750 °C in 50 °C increments on the gasification product gas at mass-based equivalence ratios of 0.15 and 0.2 was studied. To explore the potential of torrefied biomass, the gasification results were compared to that of the 'as received' biomass. The product gas from torrefied biomass produced higher H 2 , CO and CH 4 concentrations at identical oxidant flow rates in addition to higher cold gas efficiency and higher product gas heating value. The influence of equivalence ratio in gasification was also investigated at reactor temperatures of 750 °C and five equivalence ratios (0.15, 0.2, 0.25, 0.3, and 0.35). The results revealed that the torrefied biomass has the highest HHV at an equivalence ratio of 0.2 with a value of 6.09 MJ/Nm 3 , while 'as received' biomass 4.72 MJ/Nm 3 . Kinetic experiments under isothermal conditions were performed for the gasification of the materials in continuous mode. A mass balance model was successfully used to provide the capability of separately determining the rate constant of the reactions taking place. The kinetic parameters were calculated by a first order reaction model giving activation energies for 'as received' olive kernels of 84 kJ/mol and for torrefied olive kernels of 106 kJ/mol.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetics and Performance of Raw and Torrefied Biomass in a Continuous Bubbling Fluidized Bed Gasifier

Al-Farraji

Marsh

Steer

et al. 2017

Waste Biomass Valor

View full text Add to dashboard Cite

show abstract

“…The kinetic parameters represented by the order of reaction or the activation energy may be so misleading that, if used in scaling up, it may result in problems with plant operation. It is therefore essential to make a careful study of the interaction to eliminate physical effects from purely chemical processes [14]. The pyrolysis of biomass involves the transport of gas and heat from the external bulk gas phase to the internal particle surface, where the chemical reactions take place.…”

Section: Introductionmentioning

confidence: 99%

A Comparison of the Pyrolysis of Olive Kernel Biomass in Fluidised and Fixed Bed Conditions

Al-Farraji

Marsh

Steer

2016

Waste Biomass Valor

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The use of thermogravimetric analysis to describe biomass kinetics often uses bench top thermogravimetric analyser (TGA) analysers which are only capable of low heating rates. The aim of this research was to compare experimental fast pyrolysis of Olive kernels in a bespoke laboratory thermogravimetric fluidised bed reactor (TGFBR) characterised by rapid heating rates at high flow rates, compared to a smaller bench scale fixed bed TGA system. The pyrolysis in the TGFBR was analysed by using the isothermal kinetic approach and it was theorised that the pyrolysis decomposition reactions occurred by two mechanisms depending on the temperature, resulting in an activation energy of 67.4 kJ/mol at temperatures below \500°C and 60.8 kJ/mol at temperatures [500°C. For comparison, a bench scale TGA was used to look at the thermal behaviour in different fixed bed thermal conditions giving a higher activation energy of 74.4 kJ/mol due to the effect of external particle gas diffusion. The effect of biomass particle size (0.3-4.0 mm) on the conversion of biomass at different temperatures, was investigated between 300 and 660°C in the TGFBR. The results suggested inhibition of internal gas diffusion was more important at lower temperatures, but in comparison had no significant effect when measured in the fixed bed TGA at lower heating rates. Bench top TGA analysis of pyrolysis is a rapid and valuable method, but is limited by smaller sample sizes and lower heating rates. In comparison, the conditions encountered with the laboratory scale TGFBR are more likely to be relevant to larger scale systems where heat distribution, heat transfer and mass diffusion effects play major roles in the reactivity of biomass.

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“…Pore structure characteristics of activated carbons Sulfur-impregnated activated carbons are composed of a large number of micropores, and a high sulfur content enhances the adsorptive capacity of HgCl 2 by activated carbons (Ollero et al, 2002). Micropores usually possess the majority of active sites for HgCl 2 adsorption, whereas macropores and mesopores act as transportation routes .…”

Section: Resultsmentioning

confidence: 99%

Enhanced mercuric chloride adsorption onto sulfur-modified activated carbons derived from waste tires

Yuan

Wang

Xue

et al. 2012

Journal of the Air & Waste Management Association

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Diffusional effects in TGA gasification experiments for kinetic determination

Cited by 163 publications

References 8 publications

Kinetics and Performance of Raw and Torrefied Biomass in a Continuous Bubbling Fluidized Bed Gasifier

Kinetics and Performance of Raw and Torrefied Biomass in a Continuous Bubbling Fluidized Bed Gasifier

A Comparison of the Pyrolysis of Olive Kernel Biomass in Fluidised and Fixed Bed Conditions

Enhanced mercuric chloride adsorption onto sulfur-modified activated carbons derived from waste tires

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